driconf: Add ignore_discard_framebuffer option

Some apps use glDiscardFramebuffer()/glInvalidateFramebuffer() when they
only kidding.  Add a knob to disable that.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Mike Blumenkrantz <michael.blumenkrantz@gmail.com>

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21916>

src/gallium/auxiliary/pipe-loader/driinfo_gallium.h

@@ -52,6 +52,7 @@ DRI_CONF_SECTION_DEBUG
    DRI_CONF_FORCE_DIRECT_GLX_CONTEXT(false)
    DRI_CONF_ALLOW_INVALID_GLX_DESTROY_WINDOW(false)
    DRI_CONF_KEEP_NATIVE_WINDOW_GLX_DRAWABLE(false)
+   DRI_CONF_IGNORE_DISCARD_FRAMEBUFFER(false)
 DRI_CONF_SECTION_END
 
 DRI_CONF_SECTION_MISCELLANEOUS

src/gallium/auxiliary/util/u_driconf.c

@@ -64,6 +64,7 @@ u_driconf_fill_st_options(struct st_config_options *options,
    query_bool_option(allow_draw_out_of_order);
    query_bool_option(glthread_nop_check_framebuffer_status);
    query_bool_option(ignore_map_unsynchronized);
+   query_bool_option(ignore_discard_framebuffer);
    query_bool_option(force_gl_names_reuse);
    query_bool_option(force_gl_map_buffer_synchronized);
    query_bool_option(transcode_etc);

src/gallium/include/frontend/api.h

@@ -192,6 +192,7 @@ struct st_config_options
    bool allow_draw_out_of_order;
    bool glthread_nop_check_framebuffer_status;
    bool ignore_map_unsynchronized;
+   bool ignore_discard_framebuffer;
    bool force_integer_tex_nearest;
    bool force_gl_names_reuse;
    bool force_gl_map_buffer_synchronized;

src/mesa/main/fbobject.c

@@ -5386,6 +5386,9 @@ discard_framebuffer(struct gl_context *ctx, struct gl_framebuffer *fb,
 {
    uint32_t mask = 0;
 
+   if (unlikely(ctx->st_opts->ignore_discard_framebuffer))
+      return;
+
    for (int i = 0; i < numAttachments; i++) {
       GLenum att = attachments[i];
 

src/util/driconf.h

@@ -306,6 +306,10 @@
    DRI_CONF_OPT_B(no_16bit, def, \
                   "Disable 16-bit instructions")
 
+#define DRI_CONF_IGNORE_DISCARD_FRAMEBUFFER(def) \
+   DRI_CONF_OPT_B(ignore_discard_framebuffer, def, \
+                  "Ignore glDiscardFramebuffer/glInvalidateFramebuffer, workaround for games that use it incorrectly")
+
 /**
  * \brief Image quality-related options
  */